1. Field of the Invention
The present invention relates generally to automotive occupant restraint systems, and more specifically to the construction of mechanisms for providing condition responsive pretensioning force to the buckle end of the automotive seat belt systems.
2. Description of Related Art
It is well-known in the automotive industry to provide pretensioning devices for enhancing the efficacy of occupant restraint systems that employ seat belts. In one particular type of pretensioning device, a pyrotechnic gas generator is employed to drive the end of a cable supporting a seat belt buckle in response to a predetermined deceleration of the vehicle in which the buckle is installed. U.S. Pat. No. 5,403,037 is exemplary of such pretensioning devices. One important design constraint in providing such a pretensioner is to provide a housing for accommodating the travel of the mechanism that is displaced by the gases in the pyrotechnic device. This space for travel must be provided in the design of this automotive component with regard to the overall desire of designers and manufacturers of automobiles to minimize the weight and cost of the components used in the assembly of the vehicle. Since the movement that must be accommodated is not normal and repetitive movement in the use of occupant restraint systems, but rather is emergency condition responsive, it is particularly true that the weight and cost of the component incurred through the provision of such space be of particular importance. It has been found that the cost and weight of such a pretensioning device may be improved through the design of a housing that permits movement of a portion of the pretensioning structure including a structure attaching it to the seat belt system outside of the housing of the pretensioner itself.
It is also a design constraint in such designs to economically and effectively seal the movable components of the pretensioner from the surrounding vehicle environment.